1. Field of the Invention
The present invention relates to a single-track roller skate comprising at least three wheels which are disposed one behind the other, the rolling faces of which comprise in the cross-section substantially identical curvatures and are designed symmetrically with respect to the longitudinal central plane, wherein the wheels with respect to a planar contact surface contact said contact surface both in a vertical and also inclined position. The present invention likewise relates to a set of wheels (set) and to a front or rear wheel and to a central wheel for use in such a roller skate.
2. Description of the Prior Art
Wheels for single-track roller skates which are commercially available are constructed from a single piece rim body for the purpose of receiving a ball bearing for the axle pin and from a tire body which is attached to the rim body and which is manufactured in one piece from a synthetic material (See for example U.S. Pat. No. 5,048,848).
Technical literature does, however, also describe wheels comprising a different construction which mainly comprise a combination of a harder material with a softer material. For example, DE 628 872-C describes two wheels, the wheel bodies of which comprise a softer outer and a harder inner rubber ring. GB 1 585 942 describes such a wheel for use on a dual-track roller skate or a skate board. DE 1 578 776-B illustrates a wheel for a dual track roller skate wherein an annular recess is provided on the lateral outer surface of the tire body. U.S. Pat. No. 4,699,432 describes a wheel, wherein a hard tire body is provided along its rolling face with a plurality of recesses which are filled with a relative soft material in order to be able to absorb better any irregularities in the ground surface. DE 228 679-C describes a metal running ring, consisting of a plurality of layers of differing hardness, for ball bearings or roller bearings. DE 908 232-C describes a wheel, wherein an inner hub ring and an outer running ring, which are manufactured from a metal, are mutually connected in a radial manner by way of an elastic interpositioned ring, in order to be able to transmit the pressure in a uniform manner. Moreover, DE 2 250 880-A describes a wheel, wherein a metal ring is cast as one into the wheel body consisting of a synthetic material and said metal ring forms a rolling face when protruding radially over the synthetic material body, in order to be able to use the roller on flat surfaces, e.g. on ice. Wheels for roller skates comprising a profiled running face are described inter alia in DE 1 031 192-C and DE 1 199 172-C, wherein in the former the profile is filled with a soft material. EP 652 035-A1 describes a roller skate, the wheels of which are composed of three discs, wherein the central disc is manufactured from a material having a low coefficient of friction (hard) and the lateral discs disposed on both sides of the central disc are manufactured from a material having a high coefficient of friction (soft). As a consequence, the lateral discs are used for the purpose of braking the roller skate.
Furthermore, it is generally already known to offer wheels for roller skates in sets of four or eight identical wheels, wherein the different sets comprise a different degree of (Shore-A) hardness. For example, in the brochure "Krypto Feeling" (available from the ISPO 1982) wheels for dual-track roller skates having a Shore hardness 78 A, 88 A, 92 A and 96 A are offered in order to adapt the roller skate to different applications, e.g. road, sports hall or disco. FR 2 606 654 describes a Shore hardness range from 35 to 100 for wheels.
Fundamentally, however, in the case of all above mentioned known roller skates (mainly four) identical wheels are used.
In order to steer single-track steerable roller skates, fundamentally three different steering methods are known, of which two are commercially available.
In the case of the most frequently used system, at least two non-identical widely protruding wheels can be mounted in a wheel sequence within a U-shaped frame, whereby the so-called "rockering effect" is created. (See for example the above mentioned U.S. Pat. No. 5,048,848 and FR 2 606 654). Although these roller skates can be easily steered, they do, however, suffer from a so-called rockering effect which renders the device unsafe for beginners and travel in a straight line becomes unsteady and unstable, so that according to the recommendation of the experts said roller skates should only be used in this arrangement by experienced skaters.
The other type of steering consists of a kinematic wheel suspension, which in the case of an inclination together with the loading by the skater controls the wheels! in the direction of the inclination. The disadvantage of this arrangement is the relative weight dependency of the steering torque release, which should be fixed by means of a precise adjustment. Experience shows that owing to the time involved such an adjustment is, however, omitted. If this steering system also only reacts in association with the direction, considerably greater safety standards are demonstrated, as all wheels remain in constant contact with the ground and this steering system can therefore also be used readily for beginners.
The little known type of steering system which is unavailable commercially relates to a roller skate comprising three wheels, of which the central and front or rear wheel have different wheel cross-sections. This steering system has not become popular, since owing to the three wheel arrangement it is less stable and therefore intended more for practised skaters. This particularly applies within the inclined position in curves, which in any case require more skill. A steering system of this type is described inter alia in U.S. Pat. No. 2,570,349 (Kardhordo). This system was moreover operational at a time when roller skate wheel technology by no means allowed the travel comfort available nowadays and therefore skating was limited to special places and sports halls.
A roller skate of an improved design in contrast thereto is known from WO 95/30461 (MRK Handels-AG). This single-track roller skate comprises at least three wheels disposed one behind the other, the rolling faces of which are disposed in a symmetrical manner with respect to the longitudinal central plane and comprise in the cross-section substantially identical curvatures. In the case of one embodiment the wheel body comprises a higher degree of elasticity by virtue of forming a groove in the region of the transitional edges, so that when tilted towards the side the rolling face is deformed with respect to the wheel axis by means of the weight of the roller skater in the sense of a greater curvature and a good base contact is also achieved in this case.